(In reply to comment #2)
> Hello Alex,
> 
> Thanks for replying to my bug report.
> 
> I am not certain exactly when this bug was introduced or even which
> component is involved, but since TF2 was stable a month ago it must be a
> regression.
> 
> I can report that having played well over 2 h with dynamic power management
> disabled, that this bug is related to dpm.
> 
> However, playing with radeon.dpm=1 and setting
> /sys/class/drm/card0/device/power_dpm_state to 'balanced' (down from
> 'performance'), the stalls become much less frequent, more in the range of
> once or twice every 2-3 hours.

I think it's coincidence.  balanced and performance are the same on your chip.